Patent attributes
A constant ratio current source comprises a first current branch which includes a first transistor that conducts a current I1 from a first current input to a first node and a resistor R1 connected between the first node and a circuit common point, and a second current branch which includes a second transistor that conducts a current I2 from a second current input to a second node and a resistor R2 connected between the second node and the circuit common point. The current branches are arranged such that I2 varies with I1. A linear negative resistance circuit connected between the first and second nodes provides an apparent negative resistance that increases the differential output impedance at the first and second current inputs, such that the ratio of I2:I1 is maintained approximately constant for a varying differential voltage applied across the first and second current inputs.
